Mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) architecture, are able to support more sophisticated services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. For example, with the improved radio interface and enhanced data rates provided by LTE systems, a user is able to enjoy high data rate applications such as video streaming and video conferencing on mobile communications devices that would previously only have been available via a fixed line data connection.
The demand to deploy fourth generation networks is therefore strong and the coverage area of these networks, i.e. geographic locations where access to the networks is possible, is expected to increase rapidly. However, although the coverage and capacity of fourth generation networks is expected to significantly exceed those of previous generations of communications networks, there are still limitations on network capacity and the geographical areas that can be served by such networks. These limitations may, for example, be particularly relevant in situations in which networks are experiencing high load.
Consequently, there is a demand to deploy fourth generation networks in resources conventionally allocated to preceding mobile communications system such as GSM mobile communications systems. However, although the network operators wish to increase the deployment of fourth generation networks, they also wish to maintain the presence of GSM networks for voice services and low-cost low data rate communications for example. In order to address these conflicting requirements it is envisaged that portions of resources conventionally allocated GSM systems and the like may be used for the deployment of fourth generation network.